Left ventricular wall stress in compensated aortic stenosis in children

Congenital Aortic Valve Stenosis

Aortic valve stenosis in children is a congenital heart defect that causes fixed form of hemodynamically significant left ventricular outflow tract obstruction with progressive course. Neonates and young infants who have aortic valve stenosis, usually develop congestive heart failure. Children and adolescents who have aortic valve stenosis, are mostly asymptomatic, although they may carry a small but significant risk of sudden death. Transcatheter or surgical intervention is indicated for symptomatic patients or those with moderate to severe left ventricular outflow tract obstruction. Many may need reintervention.

Evaluation and Management of Aortic Stenosis for the Emergency Clinician: An Evidence-Based Review of the Literature

INTRODUCTION

Aortic stenosis is a common condition among older adults that can be associated with dangerous outcomes, due to both the disease itself and its influence on other conditions.

OBJECTIVE

This review provides an evidence-based summary of the current emergency department (ED) evaluation and management of aortic stenosis.

DISCUSSION

Aortic stenosis refers to significant narrowing of the aortic valve and can be caused by calcific disease, congenital causes, or rheumatic valvular disease. Symptoms of advanced disease include angina, dyspnea, and syncope. Patients with these symptoms have a much higher mortality rate than asymptomatic patients. Initial evaluation should include an electrocardiogram, complete blood count, basic metabolic profile, coagulation studies, troponin, brain natriuretic peptide, type and screen, and a chest radiograph. Transthoracic echocardiogram is the test of choice, but point-of-care ultrasound has been found to have good accuracy when a formal echocardiogram is not feasible. Initial management should begin with restoring preload and ensuring a normal heart rate, as both bradycardia and tachycardia can lead to clinical decompensation. For patients with high blood pressure and heart failure symptoms, nitrate agents may be reasonable, but hypotension should be avoided. Dobutamine can increase inotropy. For hypotensive patients, vasopressors should be used at the lowest effective dose. The treatment of choice is valve replacement, but extracorporeal membrane oxygenation and percutaneous balloon dilatation of the aortic valve have been described as temporizing measures.

CONCLUSION

Aortic stenosis is an important condition that can lead to dangerous outcomes and requires prompt recognition and disease-specific management in the ED.

Tachycardiomyopathy complicated by focal atrial tachycardia: incidence, risk factors, and long-term outcome

OBJECTIVE

Focal atrial tachycardias (ATs) are known to have the potential to develop tachycardiomyopathy (TCM). The aim of the study was to investigate the incidence, risk factors, and long-term outcome of TCM patients complicated by focal ATs.

METHODS AND RESULTS

A total of 237 patients undergoing electrophysiological studies were enrolled, among which 216 patients were diagnosed as focal ATs. In total, 18 patients (8.3%, 13 males) were identified to have TCM. The TCM patients were younger (29.8 ± 20.1 vs. 45.9 ± 17.3; P < 0.000) and were more frequently males (13/18 vs. 80/198; P = 0.014). The ATs were more likely to be persistent (11/18 vs. 32/198; P < 0.001). There was no difference between the 2 groups in terms of the tachycardia cycle length (392 milliseconds vs. 380 milliseconds; P = 0.56) and heart rate (144 bpm vs. 156 bpm; P = 0.15). The persistence and incidence of symptoms and prevalence of structural heart disease were comparable between the groups. In a multivariable analysis, the younger age and persistent nature were independently associated with TCM. In a 56 ± 21-month follow-up, all TCM patients had improved left ventricle ejection fraction after successful catheter ablation or medical therapy (43.9 ± 5.8% vs. 61.1 ± 3.5%; P ＜ 0.05). However, 1 patient suffered sudden cardiac death due to unauthorized withdrawal of the drug and progressive heart failure.

CONCLUSIONS

The incidence of TCM in focal ATs patients was 8.3%. Younger age and persistent nature were the independent risk factors of TCM. Most TCM patients had a benign outcome; however, long-term risk of sudden death does exist.

Strain and strain rate echocardiography findings in children with asymptomatic congenital aortic stenosis

The aim of our study was to evaluate myocardial functions with strain/strain rate echocardiography in asymptomatic patients having congenital aortic stenosis (CAS) with normal cardiac functions as determined by conventional echocardiographic techniques and comparing them with those of healthy controls. A total of 58 patients with various degrees of isolated CAS and 52 healthy controls were enrolled in this study. Conventional and two-dimensional speckle tracking (2DSTE) echocardiography were performed. Global longitudinal strain (LS) (-23.1 ± 3.6 and -23.8 ± 4.7), and longitudinal strain rate (LSR) (-1.49 ± 0.32 and -1.76 ± 0.39) values were lower, whereas circumferential strain (CS) (-25.9 ± 4.7 and -22.8 ± 6.4) and circumferential strain rate (CSR) (-1.82 ± 0.46 and -1.69 ± 0.49) values were greater in the patient group than in the control subjects. The difference was significant for global LSR and CS (p < 0.05) values. Regional analysis showed lower LS values in the basal part of the left-ventricular (LV) free wall and lower LSR values in the basal parts of both of the septum and free wall in the patient group (p < 0.05). CS values in the anteroseptal, posterior, and inferior walls were significantly greater in the patients (p < 0.05). 2DSTE detects subtle alterations in myocardial function in asymptomatic children with CAS. Impairment of LV long-axis function occurred earlier and was more prominent in basal parts of the interventricular septum and the free wall of the left ventricle.

Aortic stenosis

In developed countries, aortic stenosis is the most prevalent of all valvular heart diseases. A manifestation of ageing, the disorder is becoming more frequent as the average age of the population increases. Symptomatic severe disease is universally fatal if left untreated yet is consistent with a typical lifespan when mechanical relief of the stenosis is provided in a timely fashion. Management of mild disease, severe asymptomatic disease, and far advanced disease, and the effect of new percutaneous treatments, provide both controversy and exciting promise to care of patients with aortic stenosis. We discuss these issues in this Review.

Two-dimensional and M-mode echocardiographic predictors of disease severity in dogs with congenital subaortic stenosis

Echocardiographic studies from 50 dogs with congenital subaortic stenosis were examined. The degree of concentric, left-ventricular hypertrophy as assessed by M-mode measurement demonstrated a positive relationship (P<0.05) to disease severity. However, the clinical utility of these measures is hindered by a large amount of individual variation (r2=0.243 to 0.473). Two-dimensional ultrasound was used to compare the cross-sectional area of the left-ventricular outflow tract to the cross-sectional area of the aortic root. The ratio of these two areas demonstrated a strong inverse relationship (P=0.001; r2=0.778) with disease severity. This ratio provides a method of estimating severity of disease by two-dimensional echocardiography.

Aortic stenosis

Valvular aortic stenosis in pediatric age group is mostly congenital in origin. The aortic valve may be unicuspid, bicuspid, tricuspid or rarely quadricuspid. Left ventricle undergoes concentric hypertrophy secondary to obstruction to its outflow tract. In neonatal aortic stenosis, left ventricle may be hypoplastic. The pathophysiology and clinical presentation vary with the age of onset and severity of obstruction. Echocardiography and Doppler are indispensible for the diagnosis of aortic stenosis and its severity. Cardiac catheterization is not necessary for the diagnosis, however it is performed as a part of balloon aortic valvuloplasty in severe cases. Balloon valvuloplasty is an effective alternative to surgery in pediatric age group. Some of these patients require surgical valve repair or replacement on follow-up. Neonates and young infants with critical aortic stenosis present with cardiogenic shock and need aggressive treatment with prostaglandin E1 infusion along with inotropic support. In experienced hands, balloon valvuloplasty is a safe procedure in neonates and infants with critical stenosis. Patients with mild and moderate aortic stenosis may be left on medical follow-up.

[Wall tension or stress in ischemic heart disease]

INTRODUCTION

Wall stress or wall tension is a conception derived from physics (Laplace's law) and represents the systolic force or work per surface unit. It is the systolic force made by myocardial tissues. Stress increase indicates enlargement of the left ventricle or increase of intracavitary pressure.

MATERIAL AND METHODS

This investigation included 170 subjects; control group consisted of 50 patients (pts) with normal coronary angiographic finding without valvular anomalies and the examination group included 120 pts with coronary disease. Transthoracic echocardiography was performed in the left lateral position using computerized Hewlett Packard SONOS 1000 apparatus. Invasive hemodynamic procedure was performed using GENERAL ELETRICS CGR 300. Meridional and equatorial systolic and diastolic stress were calculated according to Grossman formula.

RESULTS

The meridional end-diastolic equatorial stress was 18.55 +/- 12.12 dyn/cm2 x 10(3) in the control group, while in coronary patients it was 28.15 +/- 13.42 dyn/cm2 x 10(3). In healthy persons the meridional end-systolic stress established by echocardiography was 190.37 +/- 23.15 dyn/cm2 x 10(3), while in coronary patients 203.82 +/- 17.88 dyn/cm2 x 10(3). End-diastolic equatorial stress was 34.32 +/- 17.18 dyn/cm2 x 10(3) in the control group and 46.13 +/- 17.82 dyn/cm2 x 10(3) in coronary patients. Systolic equatorial stress in the control group was 357.42 +/- 32.15 dyn/cm2 x 10(3) and in coronary patients 385.34 +/- 35.72 dyn/cm2 x 10(3). The same parameters determined by invasive hemodynamic procedure were slightly higher, but without statistical significance in relation to the values determined by echocardiography (P > 0.05).

CONCLUSION

Values of equatorial and particularly meridional stress were higher in coronary patients in relations to healthy persons, but without significant difference. The correlation coefficients of all investigated parameters established by noninvasive 2D echocardiography and invasive hemodynamic procedure were in one domain of medium high and high values. Meridional stress increases in coronary patients, equatorial in hypertensive patients or valvular anomalies with severe myocardial hypertrophy. In regard to high correlation between these two techniques, echocardiography may be considered a highly reliable method in evaluation of wall tension.

Maturation-dependent differences in regulation of sarcoplasmic reticulum Ca(2+) ATPase in sheep myocardium in response to pressure overload: a possible mechanism for maturation-dependent systolic and diastolic dysfunction

We have previously demonstrated that pressure-overload hypertrophy in adult sheep is associated with myocardial dysfunction whereas that in young lambs is associated with normal contractility. To probe for possible mechanisms of these age-dependent differences, we assessed mRNA expression of genes encoding critical components of myocardial Ca(2+) handling in the same animal model. We studied left ventricular myocardium of young and adult sheep with short-term (48 h) and long-term (6 wk) pressure overload induced by ascending aortic constriction. Six weeks of pressure overload induced the significant left ventricular hypertrophy (36 and 39% increase in left ventricular/body weight ratio in lambs and sheep, respectively). The Ca(2+) ATPase and Na(+)/Ca(2+) exchanger mRNA decreased with pressure overload only in the adult (p < 0.05). Ca(2+) channel mRNA was slightly increased by pressure overload regardless of age (p < 0.05). Calsequestrin, sarcoplasmic reticulum Ca(2+) release channel, or myosin heavy-chain mRNA levels did not significantly differ. In adult sheep after 6 wk of pressure overload, decreases in load-adjusted midwall shortening (systolic dysfunction) and prolongation of relaxation time constant (diastolic dysfunction) correlated with decreases in Ca(2+)-ATPase mRNA. The sarcoplasmic reticulum Ca(2+)-ATPase protein level and Ca(2+) uptake activity of isolated sarcoplasmic reticulum vesicles were depressed only in the adult with pressure-overload hypertrophy but not in the young. We demonstrated age-dependent differences in mRNA expression of Ca(2+)-handling protein genes in response to pressure overload, which preceded the occurrence of hypertrophy and myocardial dysfunction. Thus, altered expression of Ca(2+)-handling protein genes may be one of the primary responses to pressure overload rather than a phenomenon secondary to myocardial hypertrophy.

Superinhibition of sarcoplasmic reticulum function by phospholamban induces cardiac contractile failure

To determine whether selective impairment of cardiac sarcoplasmic reticulum (SR) Ca(2+) transport may drive the progressive functional deterioration leading to heart failure, transgenic mice, overexpressing a phospholamban Val(49) --> Gly mutant (2-fold), which is a superinhibitor of SR Ca(2+)-ATPase affinity for Ca(2+), were generated, and their cardiac phenotype was examined longitudinally. At 3 months of age, the increased EC(50) level of SR Ca(2+) uptake for Ca(2+) (0.67 +/- 0.09 microm) resulted in significantly higher depression of cardiomyocyte rates of shortening (57%), relengthening (31%), and prolongation of the Ca(2+) signal decay time (165%) than overexpression (2-fold) of wild type phospholamban (68%, 64%, and 125%, respectively), compared with controls (100%). Echocardiography also revealed significantly depressed function and impaired beta-adrenergic responses in mutant hearts. The depressed contractile parameters were associated with left ventricular remodeling, recapitulation of fetal gene expression, and hypertrophy, which progressed to dilated cardiomyopathy with interstitial tissue fibrosis and death by 6 months in males. Females also had ventricular hypertrophy at 3 months but exhibited normal systolic function up to 12 months of age. These results suggest a causal relationship between defective SR Ca(2+) cycling and cardiac remodeling leading to heart failure, with a gender-dependent influence on the time course of these alterations.

Usefulness of Parameters of Left Ventricular Wall Stress and Systolic Function in the Evaluation of Patients with Aortic Stenosis

Left ventricular function and myocardial contractility in aortic stenosis have been intensely studied over the past 40 years. The underlying impetus for a good deal of this work has been to define the interaction between the ventricle and the valve, to predict in an individual patient the clinical course and outcome after aortic valve replacement. Furthermore, the relationship between afterload (wall stress) and contractility has been closely examined. Although wall stress has been shown to be inversely correlated to ejection fraction or fiber shortening, there is wide individual variability for a similar degree of valvular stenosis, which renders interpretation of data regarding left ventricular function and myocardial contractility difficult. A number of other factors affect the response of the left ventricle to chronic pressure overload. The use of stress-shortening relationships in patients with aortic stenosis requires further study before these measures can be advocated for clinical use. This review examines the usefulness of left ventricular wall stress and parameters of left ventricular function in aortic stenosis, dealing with basic concepts, echocardiographic approach, and clinical usefulness.

An adult canine model of progressive left ventricular pressure overload

This article details the development of a model of progressive left ventricular pressure overload (LVPO) in the adult dog. LVPO was induced by banding the proximal ascending aorta in 69 adult conditioned dogs. The base of the aorta was exposed through a right thoracotomy. A tunnel was created by blunt dissection between the aorta and pulmonary arteries. An aortic band was constructed by passing umbilical tapes through the lumen of gortex tubing. This band was placed through the tunnel, then tied around a balloon dilatation catheter. The distal end of the balloon catheter was closed with an injection cap and positioned in a subcutaneous pocket. Aortic stenosis was induced by filling the balloon catheter with saline. A predetermined amount of LVPO was created by adjusting the amount of aortic stenosis. At 2, 4, and 6 weeks after aortic banding the LVPO was increased by transcutaneous injection of saline into the balloon catheter. At 8 weeks the dogs were evaluated for sufficiently decreased cardiac contractility and used acutely in one of several studies. The article also discusses perioperative management, postoperative care, and complications that were encountered during the development of the model. Postoperative pain was managed by the combined use of preemptive and postoperative opioids, local nerve blocks, and nonsteroidal anti-inflammatory drugs. Notable intraoperative complications included atrial and ventricular arrhythmias and pulmonary artery laceration during the banding procedure. The most significant postoperative complications were aortic ruptures and congestive heart failure. The success rate of this model has increased from 20% (year 1) to 65% (year 3). This success has been attributed to improvements in band design, surgical technique, and postoperative management.

Premorbid determinants of left ventricular dysfunction in a novel model of gradually induced pressure overload in the adult canine

BACKGROUND

When a pressure overload is placed on the left ventricle, some patients develop relatively modest hypertrophy whereas others develop extensive hypertrophy. Likewise, the occurrence of contractile dysfunction also is variable. The cause of this heterogeneity is not well understood.

METHODS AND RESULTS

We recently developed a model of gradual proximal aortic constriction in the adult canine that mimicked the heterogeneity of the hypertrophic response seen in humans. We hypothesized that differences in outcome were related to differences present before banding. Fifteen animals were studied initially. Ten developed left ventricular dysfunction (dys group). Five dogs maintained normal function (nl group). At baseline, the nl group had a lower mean systolic wall stress (96 +/- 9 kdyne/cm2; dys group, 156 +/- 7 kdyne/cm2; P < .0002) and greater relative left ventricular mass (left ventricular weight [g]/body wt [kg], 5.1 +/- 0.36; dys group, 3.9 +/- 0.26; P < .02). On the basis of differences in mean systolic wall stress at baseline, we predicted outcome in the next 28 dogs by using a cutoff of 115 kdyne/cm2. Eighteen of 20 dogs with baseline mean systolic stress > 115 kdyne/cm2 developed dysfunction whereas 6 of 8 dogs with resting stress < or = 115 kdyne/cm2 maintained normal function.

CONCLUSIONS

We conclude that this canine model mimicked the heterogeneous hypertrophic response seen in humans. In the group that eventually developed dysfunction there was less cardiac mass despite 60% higher wall stress at baseline, suggesting a different set point for regulating myocardial growth in the two groups.

Severe aortic stenosis without left ventricular hypertrophy: prevalence, predictors, and short-term follow up after aortic valve replacement

OBJECTIVES

The purpose of the present study in patients with severe aortic stenosis was to assess the prevalence of absent left ventricular hypertrophy (LVH) (determined according to mass criteria), to identify predictors of absent LVH, and to assess short-term left ventricular adaptation and prognosis after aortic valve replacement.

METHODS

Left ventricular mass (LVM) was determined by echocardiography in 109 men and 101 women with severe aortic stenosis (mean pressure gradient < or = 50 mm Hg). LVH was defined as LVM > or = 109 g/m2 in women and LVM > or = 134 g/m2 in men.

RESULTS

One hundred and eighty nine patients showed LVH (group 1) (90%; mean (SD) age 65 (14) years), and 21 showed no LVH (group 2) (10%, age 57 (21) years P = 0.02 for difference in age). Twelve (6%) of those without LVH had increased relative wall thickness (that is, > or = 0.45 with LV concentric remodelling) and nine (4%) showed no macroscopically detectable hypertrophic adaptation. The following variables were associated with the absence of LVH: low body surface area, low body mass index, and increased cardiac index. 76/210 patients were followed up a mean of six months after aortic valve replacement. The frequency of adequate ventricular adaptation to the decreased afterload after aortic valve replacement was higher in patients with LVH than in those without. Mortality six months after aortic valve replacement was lower, but not significantly, in patients with LVH (7.6%) than in those without LVH (12.5%, P = 0.10).

CONCLUSIONS

A tenth of patients with severe aortic stenosis did not develop LVH according to mass criteria; 4% of the patients did not have any macroscopic signs of myocardial adaptation to the pressure overload despite longstanding disease. Small body size was independently associated with lack of LVH according to mass criteria. Six months after aortic valve replacement, ventricular adaptation was more often adequate in patients with LVH than in those without.

Effect of increased wall thickness on indices of left ventricular pump function in children

OBJECTIVE

To investigate whether augmented chamber performance in children with a concentric hypertrophied left ventricle is due to increased myocardial shortening or a geometric effect of the thickened ventricular wall.

DESIGN

Chamber performance in terms of fractional area change and myocardial shortening--that is, circumferential midwall shortening--were measured by cross sectional echocardiography in young people with normal left ventricles and those with concentric hypertrophy of the left ventricle.

PATIENTS

52 healthy infants, children, and young people (age range 3 1/2 weeks to 26 years; body weight 1.8-89 kg (mean 23.6 kg)) and 29 infants, children, and adolescents with ventricular hypertrophy (mean body weight 31.4 kg, age range 4 weeks to 18.7 years).

MAIN OUTCOME MEASURES

Chamber areas, fractional area change, midwall circumferential shortening normalised to body weight.

RESULTS

In the controls normalised reference values were: end diastolic cavity area, 1.47 (0.25) cm2/kg0.65; fractional area change, 0.56 (0.03); end diastolic myocardial area, 1.62 (0.25) cm2/kg0.55; midwall circumferential shortening, 0.21 (0.03). By comparison, the patients had normal chamber areas (end diastolic myocardial area, 1.57 (0.42) cm2/kg0.65), increased fractional area change, 0.68 (0.05) (P < 0.001), and normal midwall circumferential shortening, 0.21 (0.03). There was a significant relation between the degree of hypertrophy (in terms of end diastolic myocardial area) and pump function while midwall shortening remained constant: 0.08 x end diastolic myocardial area + 0.44 (r = 0.74, P < 0.001).

CONCLUSIONS

The relation between myocardial shortening, wall thickness, and fractional area change emphasises that the augmentation of pump function variables in left ventricular hypertrophy in young people is an effect of the thickened wall and not necessarily due to increased myocardial shortening. This relation offers the possibility of assessing the adequacy of chamber performance with respect to the degree of hypertrophy.

Effect of chronic supraventricular tachycardia on left ventricular function and structure in newborn pigs

OBJECTIVES

The purpose of this study was to examine the effects of supraventricular pacing tachycardia on left ventricular function and myocardial structure in newborn, immature pigs and to determine whether immature pigs respond to supraventricular tachycardia differently from adults.

BACKGROUND

Previous studies have shown that supraventricular tachycardia causes dilated cardiomyopathy in adult animals; however, in humans, supraventricular tachycardia-induced congestive heart failure occurs most frequently in children and newborns. Because some clinical diseases may cause myocardial failure in adults but rarely do so in children, it was hypothesized that the effects of supraventricular tachycardia in newborns may be different from those in adults.

METHODS

In two groups of newborn swine (3 weeks of age), left ventricular volume, mass and function were assessed with simultaneous echocardiography and cardiac catheterization and myocardial structure was examined with light and electron microscopy. Six piglets underwent 3 weeks of left atrial pacing tachycardia (240 beats/min) and six littermates served as a control group. Both groups were followed up for 3 weeks.

RESULTS

At the end of the protocol, left ventricular dimensions increased in the piglets with supraventricular tachycardia compared with values in the control group, but there were no differences in left ventricular mass. Systolic function, assessed by fractional shortening, peak ejection rate and maximal rate of pressure development, was decreased in the group with supraventricular tachycardia. The fractional shortening-end-systolic stress relation in the piglets with supraventricular tachycardia decreased below normal values. Left ventricular diastolic function assessed by the relaxation time constant was prolonged, the peak filling rate was decreased and left ventricular stiffness was increased in the supraventricular tachycardia group. The morphologic data demonstrated that supraventricular tachycardia did not change total myocyte volume but did decrease total myofibrillar volume.

CONCLUSIONS

Supraventricular tachycardia caused dilated cardiomyopathy in immature pigs. These changes in left ventricular function were associated with a decrease in cellular contractile proteins. Thus, the effects of supraventricular tachycardia on left ventricular function and structure in immature animals were comparable to previous findings in mature animals.

Sex-associated differences in left ventricular function in aortic stenosis of the elderly

BACKGROUND

In aortic stenosis, the response of the left ventricle to pressure overload varies from compensated hypertrophy to overt heart failure. The determinants of left ventricular adaptation are poorly understood.

METHODS AND RESULTS

Left ventricular function was compared to assess the role of sex in 34 women and 29 men 60 years or older with both hemodynamic and echocardiographic data characteristic of severe aortic stenosis and no important coronary artery disease. Despite a similar degree of left ventricular outflow obstruction in women versus men (aortic valve area 0.54 +/- 0.20 versus 0.59 +/- 0.19 cm2, NS), the left ventricle of women had a greater fractional shortening (37 +/- 12 versus 25 +/- 12%, p = 0.001), achieved a smaller end-systolic chamber size (1.82 +/- 0.64 versus 2.17 +/- 0.65 cm/m2, p = 0.04), and generated more pressure (210 +/- 35 versus 182 +/- 29 mm Hg, p = 0.001) with a greater maximum positive dP/dt (2.153 +/- 794 versus 1,595 +/- 384 mm Hg/sec, p = 0.02). The men had a lower cardiac index (2.12 +/- 0.59 versus 2.49 +/- 0.63 l/min/m2, p = 0.02), higher mean pulmonary artery pressure (35 +/- 13 versus 27 +/- 10 mm Hg, p = 0.01), and shorter ejection period (340 +/- 40 versus 370 +/- 40 msec, p = 0.02). Women and men were equally symptomatic. Supernormal left ventricular ejection performance was present in 41% of the women and only 14% of the men (p = 0.002). This subgroup of women had a small, thick-walled chamber (end-diastolic radius to thickness ratio, 1.58 +/- 0.52 versus 2.45 +/- 0.51 in control women, p = 0.01) with low end-systolic wall stress. Subnormal ejection performance was present in 64% of the men and only 18% of the women (p = 0.002). This subgroup of men had an increased chamber size and high end-systolic wall stress compared with control men. Greater left ventricular mass was present in men compared with women (211 +/- 55 versus 179 +/- 55 g/m2, p = 0.03).

CONCLUSIONS

Sex is a factor in left ventricular adaptation to valvular aortic stenosis in adults 60 years or older.

Pulmonary autograft replacement in children. The ideal solution?

Fifty-one children, aged 1.8 to 21 years (mean, 11.4) with aortic valve replacement using a pulmonary autograft are reviewed. Twenty-nine were intra-aortic implants and 22 were root replacements. There was one operative death, no late deaths, and two have required reoperation. Actuarial freedom from reoperation was 93% +/- 5.5 at 5.6 years. Freedom from progression of aortic insufficiency (AI) was 81% +/- 9 at 5.6 years in the intra-aortic implants and 86% +/- 10 in the root replacement. Enlargement of the pulmonary autograft was seen echocardiographically in both groups. This enlargement was consistent with somatic growth and not associated with progression of AI. Ten of 19 patients with aortic stenosis had an LV mass index suggestive of LV hypertrophy before operation. At 1 year, 18 of 25 had a normal LV mass index. Thirteen of 16 patients with AI had preoperative abnormal LV mass index. All but four returned to normal by 1 year. Low operative risk, excellent function, resolution of abnormal LV hemodynamics, and enlargement consistent with somatic growth suggest that the pulmonary autograft is the ideal replacement for the malfunctioning aortic valve.

Left ventricular mass in childhood dilated cardiomyopathy: a possible predictor for selection of patients for cardiac transplantation

To determine the relationship of left ventricular hypertrophy (as assessed by mass) to symptoms and cardiac function in chronic childhood dilated cardiomyopathy, 17 long-term survivors (12 asymptomatic, 5 symptomatic) were studied at a median follow-up of 6.25 years (1.25 to 16.8 years). Left ventricular mass, dimension, wall stress, and contractility (relationship between velocity of circumferential fiber shortening and end-systolic wall stress) were assessed by echocardiography. These data were compared to measurements at the onset of disease. At follow-up, mass decreased significantly from the onset in the asymptomatic patients but remained elevated in the symptomatic patients (101 +/- 35 gm/m2 to 54 +/- 12 gm/m2, p = 0.001; 122 +/- 55 gm/m2 to 198 +/- 115 gm/m2, p = 0.23, respectively). Shortening fraction and contractility were both significantly lower in the symptomatic group compared with the asymptomatic group at follow-up (shortening fraction = 21 +/- 7% vs 29 +/- 5%, p = 0.02; contractility = -0.24 +/- 0.14 circ/sec vs -0.05 +/- 0.11 circ/sec, p = 0.01). Follow-up wall stress was slightly higher in symptomatic patients compared with asymptomatic patients. Three symptomatic patients had progressive hypertrophy and either died or required transplantation. Higher left ventricular mass is associated with the presence of symptoms, depressed contractility, and slightly higher wall stress. Persistence or progression of hypertrophy may be a poor prognostic sign in survivors of childhood dilated cardiomyopathy. Measurement of mass may be useful to indicate the necessity for closer follow-up to select patients for cardiac transplantation before hemodynamic decompensation.

Preoperative left ventricular wall stress, ejection fraction, and aortic valve gradient as prognostic indicators in aortic valve stenosis

Patients with aortic valve stenosis (AS) and left ventricular (LV) dysfunction may dramatically improve after aortic valve replacement, but operative risk is high. In an earlier study, all patients with low preoperative wall stress and low ejection fraction, or with low aortic valve gradient, died or had persistent heart failure after operation. Because wall stress is difficult to calculate, we reassessed its effect and the effect of other preoperative characteristics on outcome in 66 consecutive catheterization patients with predominant aortic stenosis referred for valve replacement. Despite ejection fraction that was inordinately low compared with afterloading wall stress in nine patients, seven patients improved with surgery. All three patients with ejection fraction less than 20% improved after surgery. Two of three patients with mean aortic valve gradients of less than 30 mm Hg improved. Mortality was 33% in patients with mean gradient less than 30 mm Hg and 19% with mean gradient less than 50 mm Hg. In the 54 patients with calculated aortic valve areas of less than or equal to 0.8 cm2, 1 (2%) had continuing heart failure, while 6 of 12 (50%, P less than .01) patients with aortic valve areas of 0.9-1.2 cm2 had continued symptoms of or died of heart failure. Patients who died or failed to improve after operation were older (71 +/- 9 years) than those who improved (65 +/- 9 years, P = .02). We conclude that wall stress calculations do not predict which patients with aortic stenosis will benefit from aortic valve replacement and that poor left ventricular function and low mean aortic valve gradient do not absolutely preclude operation. On the other hand, low gradient, non-critical valve area, and advanced age are all relative contraindications to aortic valve replacement in aortic stenosis.

Supernormal ejection performance is isolated to the ipsilateral congenitally pressure-overloaded ventricle

Congenital left ventricular pressure overload is associated with "excessive" hypertrophy that leads to subnormal afterload (wall stress), permitting enhanced ventricular ejection performance. Whether congenital right ventricular pressure overload is associated with a similar phenomenon is uncertain. It is also unknown whether supranormal ejection performance affects only the overloaded ventricle or is a general process affecting both ventricles. Conflicting data exist about whether the hypertrophic process associated with pressure overload is induced primarily by local loading conditions or by neuroendocrine influences. If the former postulate is true, the hypertrophic response should be confined to the overloaded ventricle; if the latter is true, one might predict that both ventricles would be affected by a less specific response to circulating catecholamines. To help resolve these issues, both right and left ventricular performance was examined in seven patients with isolated congenital pulmonary stenosis (average pulmonary pressure gradient 78 +/- 13 mm Hg), six patients with isolated congenital aortic stenosis (average gradient 80 +/- 10 mm Hg) and six normal subjects. Right ventricular ejection fraction was increased in patients with pulmonary stenosis (61 +/- 2%) compared with the value in normal subjects (53 +/- 2%, p less than 0.01) and in patients with aortic stenosis (50 +/- 3%, p = 0.007). Left ventricular ejection fraction was increased in patients with congenital aortic stenosis (84 +/- 4%) compared with the value in normal subjects (70 +/- 4%, p less than 0.01) and in patients with congenital pulmonary stenosis (65 +/- 2%, p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Stress-shortening relations and myocardial blood flow in compensated and failing canine hearts with pressure-overload hypertrophy

Serial changes in left ventricular (LV) size and function during the adaptation to chronic pressure overload and the transition to pump failure were studied in 16 conscious dogs (aortic bands placed at 8 weeks of age). Echocardiographic data at baseline and at 3, 6, 9, and 12 months after banding revealed a progressive increase in LV mass in all dogs. In six dogs with LV pump failure, there was a progressive decline in circumferential fiber shortening (29 +/- 4% at 12 months); this was significantly less than that seen in five littermate controls (38 +/- 3%, p less than 0.05). The average LV to body weight ratio in this group was 9.8 +/- 2.7 g/kg. In 10 dogs without pump failure (compensated LVH group), shortening exceeded that seen in the controls (43 +/- 4%, p less than 0.05); the LV to body weight ratio was 7.7 +/- 1.0 g/kg. At 12 months (cardiac catheterization), the LV end-diastolic pressure was higher in the failure (25 +/- 15 mm Hg) than in the compensated group (8 +/- 5 mm Hg, p less than 0.05); mean systolic stress was also higher in the failure group (313 +/- 67 g/cm2) than in the compensated group (202 +/- 53 g/cm2, p less than 0.05). The transmural distribution of myocardial blood flow was measured (at 12 months) with the radioactive microsphere technique; flow data were then related to an index of demand (a stress-time index). There was preferential blood flow to the subendocardial layers in the control (endo/epi = 1.28) and compensated hearts (endo/epi = 1.10), but in the failure group there was a relative decrease in subendocardial flow (endo/epi = 0.92). However, the absolute values for subendocardial flow in the normal, compensated, and failure groups were 77 +/- 54, 125 +/- 48, and 113 +/- 64 ml/min/100 g; the stress-time indexes in the subendocardial shell were 38 +/- 11, 74 +/- 19, and 93 +/- 34 g sec.10(2)/cm2/min. Despite what appears to be a marginal balance between blood flow and the stress time index in the failure group, the myocardial high energy phosphates were not depleted and the inoptropic state was not depressed. In this model of LV hypertrophy, the observed differences in fiber shortening can be explained on the basis of the inverse afterload-shortening relation; pump failure was due to an inadequate LV hypertrophy with afterload excess.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of preoperative left ventricular function with postoperative left ventricular response to exercise in patients with chronic aortic regurgitation and aortic stenosis

The relation between preoperative left ventricular (LV) systolic function at rest and postoperative LV response to exercise was assessed in 13 patients with aortic regurgitation (AR) and nine patients with aortic stenosis (AS). Preoperative end-systolic volume index (ESVI) and ejection fraction (EF) determined by LV angiography were compared with postoperative exercise-induced changes of LV fractional shortening (delta %FS) and mean velocity of fiber shortening (delta mVcf) assessed by echocardiography. Preoperative EF and ESVI in 13 patients with AR correlated well with postoperative delta %FS and delta mVcf. Similarly, preoperative EF and ESVI in nine patients with AS correlated well with postoperative delta %FS and delta mVcf. Our study demonstrated that preoperative LV systolic function in AR and AS patients closely reflected postoperative LV response to exercise. Preoperative smaller ESVI will be warranted to expect a favorably good postoperative LV response to exercise.

Alterations in left ventricular geometry, wall stress, and ejection performance after correction of congenital aortic stenosis

Children with congenital aortic stenosis have "excessive" left ventricular hypertrophy with reduced resting systolic wall stress that allows for supernormal ejection performance. If aortic stenosis is uncorrected, this pattern persists until adulthood. The effect of removing the aortic pressure gradient on left ventricular hypertrophy and wall stress in children with congenital aortic stenosis is unknown. To test the hypothesis that removal of the stimulus for hypertrophy by aortic valve replacement or repair would normalize left ventricular mass and wall stress, we measured left ventricular ejection performance, wall stress, and contractile function in seven patients at cardiac catheterization before and 36 +/- 7 months after surgical correction of congenital aortic stenosis. After aortic valve replacement or repair, the aortic valve gradient fell from 87 +/- 12 to 7 +/- 4 mm Hg, and peak left ventricular pressure fell from 187 +/- 14 to 128 +/- 8 mm Hg. Left ventricular ejection fraction decreased postoperatively from 86 +/- 4% to 74 +/- 4% (p less than 0.001), whereas velocity of circumferential fiber shortening decreased from 2.15 +/- 0.15 to 1.6 +/- 0.11 (p less than 0.002). Left ventricular mass remained unchanged preoperatively (121 +/- 14 g/m2) and postoperatively (121 +/- 16 g/m2), but wall thickness (h) decreased in relation to ventricular radius (r) (h/r = 0.55 +/- 0.05 preoperatively, 0.36 +/- 0.02 postoperatively; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Unexpected persistence into adulthood of low wall stress in patients with congenital aortic stenosis: is there a fundamental difference in the hypertrophic response to a pressure overload present from birth?

Congenital aortic stenosis in children is characterized by low left ventricular systolic wall stress allowing for supernormal ejection performance. In contrast, adults with acquired aortic stenosis have normal or excessive systolic wall stress resulting in either normal or subnormal ejection performance. In this study young children with congenital aortic stenosis, older children and adults with congenital aortic stenosis, and adults with acquired aortic stenosis were evaluated to test the hypothesis that the childhood pattern of low wall stress would convert to the adult pattern with advancing age. Left ventricular end systolic wall stress was lower in both congenital aortic stenosis groups when compared with that in age-matched normal subjects or adults with acquired aortic stenosis. Ejection fraction was higher in both groups of patients with congenital aortic stenosis than in age-matched controls. There was no tendency in the 16 patients with congenital aortic stenosis, some of whom were followed to the age of 33, for the congenital pattern of wall stress and ventricular performance to convert to the adult pattern. These results suggest that there is a fundamental difference in the hypertrophic response to a pressure overload present at birth compared with the response to one acquired later in life.

Persistent ventricular adaptations in postoperative coarctation of the aorta

To evaluate ventricular performance and myocardial contractility after surgical correction of congenital coarctation of the aorta, we studied 25 patients (16 men and 9 women, mean age 26.1 years [range 19 to 34]), an average of 10.6 years (range 2 to 25) after repair. Radionuclide ventriculography at rest and exercise and digitized, quantitative two-dimensional echocardiography were performed. Data from derived, high resolution time-activity curves by radionuclide ventriculography, combined with noninvasive hemodynamic/ventricular volume data, were compared with values in an age- and sex-matched normal population. Despite essentially identical baseline and exercise hemodynamics, postoperative coarctation subjects demonstrated enhanced ventricular contraction, as determined by the peak ejection rate at rest (-3.79 versus -3.20 stroke volume/s, p less than 0.01) and exercise (-3.00 versus -2.90 stroke volume/s, p = NS), and overall ejection fraction at rest (56.4 versus 48.0%, p less than 0.01) and exercise (70.8 versus 59.3%, p less than 0.01). An intrinsic activation-contraction delay was observed, as illustrated by a prolonged time to peak ejection rate at rest (27.7 versus 21.5% of the RR interval, p less than 0.01) and exercise (28.4 versus 21.2% of the RR interval, p less than 0.01), and total systolic time at rest (50.2 versus 43.4% of the RR interval, p less than 0.01) and exercise (56.8 versus 50.4% of the RR interval, p less than 0.01). Although left ventricular meridinal wall stress was statistically indistinguishable (62 versus 74 mm Hg/mm2, p = NS), intrinsic myocardial contractility, as assessed by the peak systolic pressure/volume ratio, was increased in the postoperative coarctation group (1.88 versus 2.87 mm Hg/ml, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of electrocardiographic and echocardiographic measures of left ventricular hypertrophy in the assessment of aortic stenosis

One hundred and nineteen patients with a clinical diagnosis of important aortic stenosis were assessed clinically and by electrocardiography and M mode echocardiography to determine the degree of left ventricular hypertrophy. Predicted left ventricular pressure was calculated from two previously described formulas. Comparisons were made between the various methods for assessing left ventricular hypertrophy to see which method most reliably predicted the severity of the stenosis as defined by invasive measurement of left ventricular pressure and peak aortic valve gradient. Direct measurement of left ventricular wall thickness from the echocardiogram, expressed as the mean of septal and posterior wall thickness, was the most accurate predictor (r = 0.75 for 29 patients with high quality echocardiograms), and surpassed derived indices (left ventricular mass (r = 0.68) and predicted left ventricular pressure derived from the two formulas (r = 0.39 and r = 0.68)) in adults. Echocardiographic results were significantly better than electrocardiographic, but only when the recordings were of very high quality. Average quality echocardiograms were no better than precordial electrocardiographic voltages for predicting the severity of aortic stenosis. The formulas for predicting left ventricular pressure were of more value in children than in adults, but they were still not sufficiently accurate to be predictive in individual cases. Electrocardiographic voltages were more accurate predictors of the severity of aortic stenosis in children than in adults.

Left ventricular hyperkinesia at rest and during exercise in normotensive patients 2 to 27 years after coarctation repair

The short- and long-term results of effective surgical repair of coarctation of the aorta on left ventricular mass and function in 48 patients were evaluated using echocardiography and stress-gated radionuclide angiography. Thirty-two of the 48 patients who had no additional cardiac problems and had technically adequate radionuclide angiograms form the basis for this report. Among these, three had mild systolic hypertension and none had significant aortic valve dysfunction. Age at the time of study ranged from 6.5 to 59 years (mean 27). Age at the time of surgery ranged from 3 months to 34 years (mean 12 years). Duration from surgery to the time of noninvasive study ranged from 2 to 29 years (mean 15). In the 32 patients, left ventricular mass was 120 +/- 20 g/m2, compared with a control value of 87 +/- 10 g/m2. Mean left ventricular ejection fraction was elevated to 69.2 +/- 1.6% at rest (control 60 +/- 1.3%) and 78.8 +/- 1.3% during exercise (control 70 +/- 1.7%) (p less than 0.01). The systolic ejection rate was significantly increased (p less than 0.01) and end-systolic volume significantly decreased (p less than 0.01) compared with values in control patients. There was no correlation between ejection fraction and either age at the time of surgery or years since surgery. These findings of hyperdynamic left ventricular function and increased left ventricular mass without apparent cause many years after coarctation repair raise important questions as to mechanisms, extension to other forms of afterload stress that have been surgically or medically relieved and long-term outcome.

Altered left ventricular mechanics in patients with valvular aortic stenosis and coarction of the aorta: effects on systolic performance and late outcome

Despite similar degrees of left ventricular systolic hypertension shortening characteristics are usually greater in patients with congenital valvular aortic stenosis (VAS) than in patients with coarctation of the aorta (CoA). We hypothesized that these dissimilarities were caused by differences in myocardial mechanics rather than by alterations in contractile state. Eleven patients with VAS (ages 6 to 41 years) and 11 with CoA were matched for age, body surface area, and peak systolic ejection gradient. Results were compared with data from 22 normal subjects matched for age and body surface area. Echocardiographic tracings of the left ventricle were recorded in conjunction with left ventricular pressure measurements (VAS) or calibrated carotid pulse tracings (CoA and normal subjects). Peak and end-systolic wall stresses as well as left ventricular shortening fraction (% delta D) and rate-corrected velocity of fiber shortening (Vcfc) were calculated. No differences for left ventricular dimensions, heart rate or peak wall stress were present. Ventricular peak systolic pressures and wall mass were higher for the patients with VAS or CoA than for the normal subjects (p less than .001). These parameters did not differ between the VAS and CoA groups. The patients with VAS had higher % delta D and Vcfc than either the CoA or normal groups (p less than .01). Afterload, as quantified by end-systolic stress, was 41% lower than normal for the patients with VAS (p less than .001) and 13% higher than normal for those with CoA (p less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Early diastolic left ventricular function in children and adults with aortic stenosis

Pressure overload hypertrophy of the left ventricle is associated with abnormal left ventricular early diastolic filling. The roles of the extent of cardiac hypertrophy, depressed left ventricular systolic function and aging in the pathogenesis of left ventricular diastolic dysfunction have not, however, been fully defined. To determine the relative importance of these factors in the pathogenesis of diastolic dysfunction in pressure overload hypertrophy, 16 children and 25 adults with aortic stenosis were compared with 48 normal children and adults, using rates of left ventricular early diastolic filling and wall thinning derived from M-mode echocardiography. Left ventricular early diastolic filling and wall thinning rates were significantly depressed in both children and adults with aortic stenosis as compared with values in normal subjects. Filling and thinning rates correlated negatively with age, left ventricular peak systolic pressure and wall thickness in all subjects. Furthermore, the effect of age on diastolic function appeared to be mediated by age-related increases in systolic pressure and wall thickness. In adults with aortic stenosis, early diastolic filling and wall thinning rates were depressed to a similar extent in subjects with normal and abnormal systolic function; thus, diastolic dysfunction does not appear to be a manifestation of abnormal systolic loading and ejection performance. These results suggest that extent of hypertrophy itself plays a dominant role in the mechanism of impaired left ventricular early diastolic filling in pressure overload due to aortic stenosis.

Left ventricular wall stress and function in childhood coarctation of the aorta

Unlike most adults with compensated pressure overload of the left ventricle, children with moderate to severe aortic stenosis exhibit pronounced left ventricular muscle hypertrophy, enhanced ejection performance and diminished wall stress. To determine whether these findings are present in other forms of left ventricular pressure overload in children, left ventricular mechanics were studied by catheterization in 14 children with coarctation of the aorta (average peak gradient 39 +/- 17 mm Hg) and in 10 normal children. Ejection fraction and mean velocity of circumferential fiber shortening in the coarctation group (0.74 +/- 0.09 and 1.71 +/- 0.43 circumferences/s, respectively) were significantly higher than in normal subjects (0.65 +/- 0.05 and 1.27 +/- 0.26 circumferences/s, respectively) (p = 0.008), but the ranges for both groups overlapped. End-systolic stress in children with coarctation (77 +/- 20 dynes X 10(3)/cm2) was less than in normal children (121 +/- 24 dynes X 10(3)/cm2) (p less than 0.001), again with overlap of the ranges for both groups. The ratio of end-systolic stress to end-systolic volume index, an estimate of contractile function, was similar in both groups. Relations between severity of obstruction (left ventricular peak systolic pressure, coarctation gradient) and end-systolic stress and between stress and ejection performance were present within the coarctation group. Comparison of these data with those found in children with moderate to severe aortic stenosis shows a similar but less pronounced response to pressure overload due to coarctation of the aorta.

Clinical improvement in hypertrophic cardiomyopathy after inferior myocardial infarction

In cases of hypertrophic cardiomyopathy, the pathophysiologic role of the systolic pressure gradient across the left ventricular outflow tract is the subject of continued controversy. A patient with this disorder is described whose symptoms and provokable intraventricular gradient disappeared after inferior myocardial infarction. Diastolic left ventricular pressures were essentially unchanged, the isovolumic relaxation period became prolonged and the ejection fraction decreased from 0.77 to 0.61 after infarction. The peak ejection rate was unchanged, but the disappearance of systolic anterior motion of the mitral valve leaflet and obstructive manifestations may have resulted from enlarged mid to late systolic ventricular volumes. This case suggests a direct relation between symptoms and intraventricular pressure gradient in certain patients with hypertrophic cardiomyopathy.

Improved prediction of peak left ventricular pressure by echocardiography in children with aortic stenosis

Prediction of peak left ventricular pressure by echocardiography in children with aortic stenosis assumes that wall stress is normal. The recent finding that stress is subnormal in many children with aortic stenosis and elevated ejection performance requires reevaluation of this noninvasive technique. By using M-mode echocardiography, left ventricular end-diastolic dimension and wall thickness and left ventricular shortening fraction were measured in 27 children with aortic stenosis undergoing left ventricular pressure measurement by cardiac catheterization. Similar echocardiographic measurements and systolic blood pressure determinations by the cuff method were obtained from 29 normal children. Peak circumferential wall stress and shortening fraction were calculated from the echocardiographic and pressure data. It was found that stress was inversely proportional to shortening fraction for all patients with aortic stenosis (p less than 0.001, r = -0.86). In a subgroup of patients with a shortening fraction of less than 0.40, stress was 262 +/- 20 mm Hg, similar to 280 +/- 30 mm Hg in the normal group but greater than 205 +/- 27 mm Hg in patients with a shortening fraction of 0.40 or greater (p less than 0.001). In patients with aortic stenosis, the ratio of left ventricular end-diastolic wall thickness to cavity dimension predicted peak left ventricular pressure moderately well (r = 0.83, standard error of the estimate [SEE] = 23). The stress-shortening fraction relation was used to estimate stress and correct this ratio in patients with diminished stress and a shortening fraction greater than or equal to 0.40. This yielded a significantly improved correlation (r = 0.93, SEE = 15, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)